2002 BMW 325 Passenger Door wont open from outside

2002 325i sedan
front passenger side door became tight and then would'nt open from outside. It opens perfectly fine from the inside.

someone told me that there is a little hook that slips out of position and needs to be placed back in position or probably tied with a ziplock or wire to present from slipping. Any clues?

I check with a servicing center and he says something is broken and it'll cost around $500-600 to fix.
Please help.